Abstract

We have made continual, multiple-day measurements of the polarization dependent loss of multiple C-band channels in an installed 1800 km terrestrial link. The PDLs of individual channels varied on the time-scale of hours, while the temporal variations of the PDLs of adjacent channels often tracked. The probability densities of the field measurements of PDL were not Maxwellian and instead were truncated, consistent with the limited number of elements in the link having appreciable PDL. A new model for the statistics of PDL in systems with few PDL elements is proposed, where a lower bound of the distribution exists if there is a dominant PDL element. The probability distributions from measurement and theory show good agreement.

Figures (4)

Schematic of transmission system and apparatus for measuring PDL of multiple WDM channels. The twelve measurement channels are denoted as λ1 to λ12. Not shown in the figure are ten WDM loading channels, distributed across the C-band, which also were added at ROADM1 and transmitted over the 1800 km looped-back link.

Normalized autocorrelations of the PDL – <PDL> for the four channels shown in Fig. 2 as a function of time delay. Solid curve is the average of the normalized autocorrelations for all 12 channels included in the histograms in Fig. 4 and is also shown in the inset.

Probability density functions of measured PDL along with the fits for the odd and even channels, shown on linear (a,b) and log scales (c,d). For the odd and even channels, the five PDL elements from the fit were 0.2201, 0.2432, 0.3504, 0.3519, and 1.4640 dB; and 0.2810, 0.2881, 0.3075, 0.3089, and 1.3264 dB, respectively. (e) Distribution of the axial component of PDL, PDLu, extracted from the data of (a-d).